The objectives of this research effort are to detemrmine whether photocoagulation therapy will be useful in preserving vision for patients with deabetic rentnopathy. The Contractor will perform the function of a participating clinical center under the national Deabetic Retinopathy Study. The study is designed to evaluate two commonly used photocoagulation techniques to determine whether photocoagulation of selected areas of the retina have a demonstrable morpholgic effect on untreated areas of the retina, etc.